Train control



May 11 1926. 1,584,225

w. K. HOW E TRAIN CONTROL Filed July 20, 1922 2 Sheets-Sheet 1 ,5 ATTORNEY W. ,K. HOWE TRAIN CONTROL 7 Filed July 20, 1922 2 Sheets-Sheet 2 b 11 h m J :2

:L I! \r m I jgVENiOR.

Patented May 11, 1926.

UNITED STATES PATENT OFFICE.

\VINTI-IROP K. HOWE, OF ROCHESTER, NEW YORK, ASSIGNOR TO GENERAL RAILWAY SIGNAL COMPANY, OF GATES, NEW YORK, A CORPORATION OF NEW YORK.

TRAIN CONTROL.

Application filed. July 20,

This invention relates to automatic speed control systems for railroads.

The present invention deals more particularly with the problem of obtaining the proper control of intermittent track devices in a danger or occupied block. After a train has reduced speed in obedience to. a caution signal and has come to a stop or to a predetermined minimum speed at the danger or stop signal, it is desirable to allow this train to proceed under proper control into the danger-block. The signal at the entrance to a stop or danger block may indicate stop due either to. the presence of another train in that block, a broken rail, open switch, or other hazard. In the interests of safety, therefore, it is desirable to enforce some minimum speed restriction upon the train as it enters and travels. through a danger block, partly so that the train can be quickly stopped as soon as the rear end of another train, open switch, or other hazard is discovered by the engineer, and partly so that a minimum damage will be done in case of r derailment due to a broken rail, or in the event of some other hazard that is not readily visible or ascertainable by the engineer. It will be evident that a danger or hazardous condition may exist in a block while the signal at the entrance to the next block in advance may indicate clear or proceed. For these reasons, among other things, it is ordinarily required by the rules that a train, entering a danger or stop block, shall proceed at a minimum speed throughout the length of this block, irrespective of the indication of the nextsignal in advance. In the event that the signal was at stop due to the presence of another train in that block, which has moved out in the meantime, it can be seen that the continued enforcement of the minimum speed restriction upon the following train becomes unnecessary and occasions useless delay.

In accordance with the present invention, speaking generally, it is proposed to provide track devices at intervals in each block which have their controlling condition dependent upon safe traffic conditions in that same block, so that these track devices may be employed to. impose a minimum restricted speed limit, in case the block is a danger block, and to remove or discontinue this speed limit as soon as the block becomes safe. In carrying out thisidea, it is, pro- 1922'. Serial N0. 576,281.,

posed to make the control of these track devices, intended to enforce or relieve the minimum speed restrictions for a danger block, dependent upon the flow of track circuit current in the track rails, so that such control determines not only the presence or absence of other vehicles or trains ahead in the same block, but also the integrity of the track rails, presence ofcars at fouling points, open switches, and other hazards- In order to disclose and explain the nature and mode of operation of the invention, it has been shown appliedto and in connection with one specific type of speed control system; but it should be understood that the invention, in its broadest aspect, is susceptible of adaptation and practical use in connection with other types of systems. In the type of system selected for the disclosure of the invention, the desired speed limits are imposed or enforced at the appropriate control points in either a caution or a danger block in accordance with a timeedistance in terval principle. More specifically, the track: elements are spaced apart on the track, preferably in. groups of three so. as to define two.- spaced intervals, one corresponding to. the caution speed limit, and the other to. the danger speed limit; and there is provided car equipment which acts to produce an. automatic brake application whenever the car traverses such spaced intervals in less. than a predetermined time, such time interval being measured either by mechanismv on the car or on the track, and the, particular spaced interval tobe effective being automatically set up: in accordance with the existence of caution or danger conditions. Also, in the particular embodiment selected for the purposes of disclosure of the in? vention, the car must be brought. to a stop after an automatic brake application has. occurred on. account of excessive speed,,before the brakes can. be released to allow the train to, proceed.

One of the principal: objects of the present invention, as indicated above, is taprovide a track device, and the proper control therefor, in. a block which may be utilized toprovide for the enforcement of a. mine. imum speed restriction and also. for the automatic discontinuation orremoval of suchrestriction. 7

Other objects; of the invention, various other characteristic features. ofthe invention, its advantages, and adaptability to practical operating conditions, pointed out hereinafter as the description of one specific embodiment progresses.

In Fig. 1 of the accompanying drawings is illustrated diagrammatically and in perspective a portion of a railway system showing one unit or group of trackway devices at a control point along the track, and suitable car-carried apparatus adapted to cooperate therewith to automatically apply the brakes of the car when different predetermined speeds for caution or stop are exceeded in passing said trackway devices; and

Fig. 2 illustrates the same trackway apparatus as shown in Fig. 1 except that three control points have been shown, it being understood that the spacing between track elements as compared with the spacing between other elements of the trackway apparatus is not strictly true on account of the difficulty in giving exact dimensions.

In the embodiment of the invention illustrated, the transmission of the desired controlling infiuences to limit the speed at several points in a block is produced by track elements which are governed in accordance with traffic conditions. Various arrangements of trackway circuits suitable for the purpose of controlling these track elements may be employed, and it should be understood that the arrangement shown in the drawing is only illustrative. Referring to the drawing, the track rails 1 and 2 of the railroad track are divided by insulated .joints 8 into blocks in the usual way, a portion of one block I and the adjacent ends of two other blocks H and J being shown. The parts and circuits associated with the various blocks are the same, and for convenience will be given like reference characters with distinctive exponents. Each of the blocks is provided with a track battery 4; and a track relay 5, the same as in ordinary block signal systems, the track rail 2, however, being further divided into sections by insulated joints 6, across each of which is connected an auxiliary relay 7. The

track circuit is thus provided with a plurality of auxiliary relays in addition to the usual track relay, one or more of which will be deprived of current by the train in a block depending on the position of the train in i said block. The invention may be used with or without the usual fixed signals Z, dependent upon the type of train control apparatus; and such fixed signals Z have been .illustrated conventionally without attempting to illustrate their well-known control circuits and devices.

In each block are provided units or groups of three track elements T at the several ,points in the block at which the speed of the train is to be checked, the spacing between will be the first element T and the third element T of each group being used to determine the distance a train is permitted to run in a predetermined time at this point in the block under caution traflic conditions, that is, when the next block in advance is occupied; and the spacing between the first track element T and the second track element T determines the distance a train is permitted to run in the same predetermined time at this point under danger traflic conditions, that is, when the same block is occupied by another train in advance of the first mentioned train. In the specific embodiment illustrated, these track elements are shown on the right side of the track when facing in the normal direction of traffic, as indicated by the arrow.

Each of these track elements T, T and T" comprises a U-shaped core 8 terminating in enlarged pole pieces 9, the back yoke of the core 8 of two of the track elements, T and T being provided with a coil 10. At each point of location of a group of trackway elements is located a repeater track or line relay 11 (only one being shown in Fig. 1), the relays 11 being connected in multiple to the line wires 12 and 13 which are energized when the track relay 5 of the block in advance is energized. From this it is readily apparent that when the block in advance is clear that each of the repeater track relays 11 will be energized, thus closing their front contacts 14 and including the coil 10 of the track element T in a closed circuit of low resistance, as is readily apparent from the drawing. The front contact 15 of each of the auxiliary relays 7 when closed connects the coil 10 of the second track element T in a similar closed circuit of low resist ance, thus causing the track element T to function like the track element T under clear or caution traffic conditions.

The car-carried apparatus of the specific embodiment of the invention illustrated comprises suitable devices which will first be separately described. One of these devices comprises an influence receiving car element L mounted on the right side of the vehicle when facing toward the front end of the vehicle so as to pass over the track elements T, T and T. This car element L consists of a U-shaped core 16, terminating in enlarged pole pieces 17, and having a primary coil P on the forward leg of the U-shaped core and a secondary coil S on the other leg. This car element L is preferably mounted directly on the truck of a railway vehicle and protected from excessive jars and vibrations, and from the weather in any suitable manner. The specific construction for the mounting of the car element L is not within the scope of the present invention, and therefore has not been illustrated.

A control relay C and a repeater relay R are provided which are particularly designed to serve the purpose for which they are intended. Although these relays have been illustrated identically, this illustration is merely conventional and the control relay C in practice is constructed with much smaller moving parts and controls smaller contacts than the repeater relay R, and will therefore function 011 a smaller change of energy. Both of these relays C and R have their moving parts well balanced so that they will not be affected by jars and vibrations, and are preferably protected from jar and vibration in a manner forming no part of this invention and not shown.

This car apparatus includes a train or brake control device K, which has been illustrated as an electro-pneumatic valve. This train control device K may control the airbrakes of the train in any suitable manner as, for instance, by venting the brake pipe when its winding 88 is deenergized. This device K is of a normally energized type, and has its normally energized circuit completed through its own front contact 18, that is, a contact controlled by its own electromagnet. Therefore, a momentary deenergization of the train control device K will permanently deenergize it, because its energizing circuit will be interrupted by its front or stick contact 18.

Another element of the car-carried apparatus embodying the present invention comprises a time control device TC. This time control device TC is provided to normally close an auxiliary circuit for the train control device K, to open this circuit a very short period after the device has been initiated, to maintain this circuit open for a predetermined time, and then again close said circuit. This time control device TC may be of any desired type, but has been shown as comprising a motor M, having an armature provided with a commutator 19, brushes 20, a shunt field winding 21, and a battery 22 permanently connected across the brushes and the shunt winding of the motor so that the motor constantly exerts torque. This motor M is preferably one of a special shunt compensated type which will maintain a constant speed irrespective of a slight variation in the voltage of the battery 22, and regardless of a slight change of load that may be applied thereto. This characteristic feature of the motor may be obtained to a large extent by proper design, and if desired a suitable speed control regulator may be incorporated therewith to give this motor a constant speed characteristic.

The motor M through the shaft 23 drives one member 2 1 of a friction clutch, the other member 25 of said friction clutch being rigidly connected to a shaft 26 provided with a worm 27. The construction of the friction clutch is such that the pressure of the spring 28 causes a frictional contact between the members 2 1 and 25, thus allowing the clutch to slip when a predetermined torque is applied between the shafts 23 and 26, but which will provide a rigid connection if a smaller torque is attempted to be transmitted from one shaft'to the other.

The Worm 27 driven by the motor M is in operative engagement with a worm wheel 29, which has fastened thereto but insulated therefrom a contact arm which is connected to one terminal of a battery B. As the worm wheel 29 is rotated in the direction or the arrow by the motor M through the intervening friction clutch, the contact arm 30 is stopped by coming in contact with a dog 31 of a time starting magnet CS. The dog 31 is connected to an armature 32 pivoted on a pin 33. As the time starting magnet CS is deenergized, a spring 34L- moves the dog 31 out of engagement with the arm 30 and allows this arm to be'rotated by the motor M through the intervening friction clutch 2 1-25.

Opemtion.Assuming that the car-carried apparatus is in its normal condition, that is, is moving between control points in a block under clear traffic conditions, when said block is not occupied by another train in advance, and when the next block in advance is clear. Under these conditions, the control relay C is maintained energized through a circuit which may be traced as follows :beginning at the terminal B of a battery which has its other terminal con nected to a common return wire N, wire front contact 40 of the control relay 0, wires 41 and 42, winding of the control relay C, wire 43, secondary coil S of the car element L, wire 4-4 back to the common return wire N.

With the control relay C in its energized position, the circuit will be completed for energizing the secondary or repeater relay B, through a circuit which may be traced as follows :beginning at the terminal B of a battery, wire 89, the other front contact 45 of the control relay C, wire 46, winding of the repeater relay R, wire 47 back to the common return wire N.

The energization of the repeater relay R closes its front contact completing the energizing circuit for the time starting magnet CS, which may be traced as follows :beginning at the terminal B of abattery, wire 18, front contacts 49 and 50 of the repeater relay R, wire 51, winding of the time starting magnet GS, wire 52 back to the common return wire N.

Another circuit which is also energized when the repeater relay R is in its energized position may be traced as follows :beginning at the terminal B of a battery, wire 48, front contact 49 of the repeater relay R, wires 53 and 54, front or stick contact 18 ot the train control device K, Wires 55 and 56, winding 38 of the train control device K, wire 57, )rimary coil P of the car element L, wire 58 back to the common return wire 1T.

An auxiliary circuit for energizing the train control device K may be traced as followsz-beginning at the terminal B of a battery, wire 59, contact arm 30 of the time control device TC, stationary contact 60, wire 61, release switch 62, wire 54, front contact 18 of the train control device K, wires 55 and 56, winding 38 of the train control device K, wire 57, primary coil 1? of the car element L, wire 58 back to the common return wire N.

The energization or the primary coil P of the car element L produces a magnetomotive-t'orce in the core of the car element, which greatly predominates over the magneto-motive-iiorce produced by the secondary coil S connected in the energizing circuit or" the control relay C, these electromotive-torces, however, being in the. same direction. This is due to the fact that the current flowing throughthe control relay C is very small, that is, is just sufiicient to maintain it in its energized position. The magneto-motive-forcc produced by the primary and secondary coils, although being cumulative, produces very little flux linking both of these coils, this being due to the large air gap between the hole pieces 17 which makes the reluctance of the magnetic circuit relatively high.

Clear tmfitc 00-n(Zz'ti0n.VVith the car apparatus in its normal condition, as just described, let us assume that the car is moving along the track so that the car element L passes over the first element T or the group of track elements under clear traffie conditions. Since this track element T is not provided with a coil, it is always in its active condition. As the car element L passes over this track element T, the reluctance hrough the core 16 of the car element is momentarily reduced. This change in reluctance causes a sudden increase of the flux linking the secondary coil S, and then a decrease o1 flux to its normal condition, partly due to a diversion of flux from leakage paths and partly due to an increase in the total flux linking or passing through the primary coil P. This sudden'increase and decrease of flux through the secondary coil S induces a voltage therein similar to that of a single cycle of alternating current E. M. F. The secondary winding S is prererably so connected with respect to the battery that the first wave of the unicycle of M. F. opposes that of the battery, thereby reducing the energizing current oi the control relay C to an extent to drop its armature by the action of the spring 63.

Since the control relay C is connected in a stick circuit, it will be permanently deenergized until again picked up by some other means, it momentarily deenergized in this manner.

The deenergization of the control relay C interrupts the energizing circuit for the repeater relay R, thus causing its armature to drop by the action of the spring 64 and interrupt one of the circuits for energizing the train control device K heretotore traced. The'other of said circuits being completed through the contact arm 30 is, however, intact and therefore the train control device K will not be deenergized. The deenergization of the repeater relay 1t closes a pick-up circuit for the control relay C, which may be traced as follows starting at the terminal B of a battery, wire 59, contact arm 30, stationary contact 60, wire 61, release switch 62, wire 53, to the back contact 65 of the repeater relay R, wires 66 and 42, Winding of the control relay C, wire 43, secondary coil S, Wire 44 back to the common return wire N. This causes the control relay 0 to again pick up, causing it to complete its previous energizing stick circuit heretofore traced, thereby again energizing the repeater relay B.

This momentary deenergization of both of the relays C and R, as just described, interrupts momentarily the normally energized circuit of the time starting magnet CS, thereby causing the dog 31 to release the contact arm 30, thus permitting the arm 30 to start on its cycle of rotation. The several devices are so designed and constructed that the auxiliary energizing circuit for the train control device K, which is carried through the contact arm 30, will not be interupted until the repeater relay R has again been energized. If only one active track element is passed over, the apparatus will function, as just described, and allow the contact arm 30 to complete its cycle of rotation and again be stopped by the dog 31 without in any way atl'ecting the train control device K, thus bringing the apparatus back to its initial and normal condition.

Assuming now that the train continues its movementalong the block and passes ver the second track element T when in its clear traiiic condition, that is, having its coil 10 closed in a circuit of low resistance through the front contact 15 of the auxiliary relay 7, as the car element L passes over the track element T only avery slight change of flux will take place through the secondary coil S of the car element. This is accounted for by the fact that a slight change of flux through the track element causes a relatively large current to be set up in the coil 10, this current being in a direction to oppose the flux producing it, thus tending to prevent a further increase of flux through the core 16 of the car element. Since only a slight change of flux takes place through the secondary coil S, due to this bucking action of the coil 10 of the track element, as just explained, the counter volt-age induced in the secondary coil S will be insufficient to decrease the current flowing through the control relay C to a value to deenergize it, and therefore the other car-carried devices will not be influenced in passing over a track element having its coil closed in a circuit of low resistance. In a similar manner the carcarried apparatus will not be actuated when passing over the third track element T" when in its clear traffic condition, thus allowing the train to proceed through the block under clear traffie conditions without the actuation of the train control device K.

Caution tmfiio c0nditi0ns.Let us assume now that a train having its car apparatus in its normal condition, as heretofore eX- plained, is passing through the block I when the next block in advance is occupied by another train. Under these traflic conditions, the track relay 5 of the block J will be deenergized because the track circuit current of the block J will flow through the wheels and axles of the train occupying the block J. This causes deenergization of the repeater track relays '11 (only one being shown in Fig. 1), thereby dropping the front contact 14, and opening the circuit through the coil 10 of the track element T thereby putting this track element in its active condition. The presence of the train in the block I will not in any way afifect the second track element T of each group as the train passes thereby, because the track circuit current flowing through the auxiliary relay 7 at the particular control point in question will still be. present because the track circuit current of the block I will flow from the track battery 4 through the rail 2, each of the auxiliary relays 7 (see Fig. 2), the front wheels and axle of the train in question back to the other rail 1, thus maintaining the track element T in its normal inactive condition. As the train moves along in the block I and passes over the first track element T, which is always in its active condition, the contact arm 30 of the time control device will be started on its cycle of rotation.

Assume first that the time consumed in running from the first track element T to the third track element T is sufiicient to allow the contact arm to complete its travel of one revolution, that is, that the train is not exceeding'the permissive speed to be enforced by the apparatus at this point. If now the third track element T is passed over, the same cycle of operation will take place without in any way affecting the train control device K. It should be borne in mind that the second track element T is in its inactive condition, and therefore does not affect the apparatus, the distance between the track element T and the insulating joint 6 being greater than the distance between the car-element L and the first axle of the train, this to assure that the train will not stop itself. I

Let us assume now that the train has just passed over the first track element T, thereby initiating the operating cycle of the contact arm 30, and that the train is moving at a rate of speed higher than that permitted by the train control apparatus, that is, that insutficient time is allowed for the contact arm 30 to reach the stationary contact 60 before L passes over T The control relay 0 and repeater relay R, respectively, will be again deenergized by the passage of the car element L over the third track element T, in the same manner as heretofore described. The deenergization of the repeater relay R will in this event interrupt the circuit through the train control device, because the auxiliary circuit is also open at the same time, since the cont-act arm 30 has not yet reached the stationary contact 60. Since the train control device K is connected in a stick circuit including the contact 18, a momentary deenergization of the train control device K will permanently deenergize it, thus applying the brakes to bring the train to a stop. The pick-up circuit for the control relay 6' will not be closed due to the making of the back contact of the repeater relay R, because there is no source of energy on the movable contact of the control relay R, the contact arm 30 not having reached the stationary contact 60. hen the contact arm 30 reaches the stationary contact 60, the pick-up circuit for the relay C heretofore traced will be completed, thusv causing it to pick up and again energize the repeater relay It. The energization of the repeater relay R closes the circuit for thetime starting magnet OS to again move the dog 31 against the stop 67, thereby stopping the rotation. of the contact arm 30 of the time control device when it has completed its cycle of rotation.

The train control device K having been deenergized, as just explained, causes the train to come to a stop automatically. In order to again proceed, it is necessary for the engineer to operate therelease switch 62. This release switch 62 may be enclosed in a locked box, the key of which is held by some other person, such as the conductor, for instance, or the release switch may only be accessible from the ground so that it f is necessary for the engineer to waitat least until the train is brought to a stop before the release switch 62 may be operated. The cirdevice of the train control device K by this release switch may be traced as follows:-

beginning at the terminal 13 of battery, wire 48, front contact 49 of the repeater relay R, wire 53, release switch 62, wires 68 and 56, winding 38 of the train control device K,'wire 57, primary coil P of the car element L, wire 58 back to the common return wire N. The train control device K having now again been energized through the energizing circuit heretofore traced, including its stick-up contact 18, the train is able to proceed under the control of the engineer.

After the release switch 62 has been actuated to re-energize the train control device K, this switch must be restored to its normal position shown, otherwise the device K will be deenergized at the next active track element, such as T, or T or T having their coils open-circuited, because with the reset switch 62 shifted to its resetting position, the auxiliary circuit for holding the device K energized while the front contact 49 of the relay R opens is broken, so that the device K is deenergized the instant relay R opens its front contact. Thus, the release switch 62 is protected against improper manipulation and can not be carelessly or maliciously left in the release position.

It should be observed that since this train control device is of a character that when two successive control influences are received in less than a predetermined time (the time required for the contact arm to make one revolution). the train control device will be actuated. Therefore, it is possible to limit the train to any particular speed by spacing the track elements Tand T a distance which the train may travel at the speed in question during the time set off by the time control devi e TC. The. operation of the automatic brake control apparatus is, therefore, dependent upon the average speed of the ve hicle between this pair of track elements. Since these track elements are located relatively close together, this average speed approximates the actualspeed when going over the second track element of such a pair.

The particular speed limit to be thus enforced or established at any given control point along the track is dependent upon the spacing of the pair of track elements T and T at that point, and by merely shortening or lengthening this spacing, the speed limit may be modified to any desired extent. Consequently, without any undue complication or expense, any desired range or value of limited speeds may be laid down or prescribed for various points in different blocks along the railroads, taking into account the conditions which cause variation in the speed limits at which automatic braking should occur. For example, variations in the length of the blocks are taken care of by spacing the pairs of track elements with respect to and in accordance with the distance they are located from the exit end of the block. Variations in the safe and proper speed limits, due to changes in grade, either up or down grade, may likewise be compensated for by selecting the location and spacing of the pairs of track elements accordingly. In short, all parts of the railroad may be engineered on their respective merits, so to speak, and the appropriate speed limits at any desired point in the several blocks may be provided, all by merely varying the space between the first and third track element for caution trafiic conditions, and like wise, if necessary, the spacing of the first and second track elements for traffic conditions in an occupied block.

Control in danger block-Let us assume now that the train in question has passed through a caution block, reducing its speed in accordance with traific conditions ahead, and enters an occupied or danger block at a reduced speed.

As explained hereinbefore, the block may be adanger block because of the presence of another car or train, a broken rail, an open switch, a car on a fouling point, or other hazardous condition. Such hazardous condition may exist in any point in the block, and may or may not be readily visible to the engineer. Hence, in the interests of safety, the minimum speed restriction should be continued throughout this danger block, irrespective of the condition of the track circuit in the next block in advance, until the danger condition is removed, such removal occurring only if every one of those conditions that is likely to make the block in question a danger block has ceased to exist. For simplicity, the danger condition in question will first be assumed to be occasioned by the presence of another train ahead in the same block. Since this block is already occupied by another train ahead, the second track element T at each of the control points between the two trains in the same block will be in its active influence transmitting condition. This is due to the fact that the track circuit current of this block flows through the wheels and axles of the preceding train, and therefore shunts all of the auxiliary relays 7 in the rear there of. The deenergization of each of these auxiliary relays 7 causes the dropping of their front contacts 15, thereby putting the second track elements T at each of said control points in their active, stopping or open-circuited condition.

As the train approaches the first control point in the occupied block, its passage over the first track element T at said control point causes the time control device TC on the car to be initiated upon its cycle of rotation. If the train passes over the second track ele ment T before the cvcle of operation of the time control device TC has been completed,

the train will be stopped in a similar manner as just described in its movement through a caution block. If, however, this time cycle of operation has been completed before the train reaches the second track element T, no such automatic brake application will take effect.

The spacing between the first and second track elements T and T, respectively, may be the same at each control point in the block to enforce a low speed limit of, say, fifteen miles per hour, or this spacing may be diderent in the same or different blocks, as desired. The spacing of the first and third track elements at each'co-ntrol point is such as to conform with the safe speed at such control point that ought to be followed by the engineer to making a speed reduction in response to a caution signal.

An important characteristic of the speed control system embodying this invention, is that any speed restrictions imposed in a caution as Well as an occupied block are instantly and automatically removed as soon as trafiic conditions ahead clear up, thereby permitting the train to accelerate, if desired, without any interference by the automatic speed control system. Thus, if the engineer sees the signal at the entrance to the next block in advance change from the stop position to either the caution or clear position, he may, even though about to pass over the track elements at a control point, release the brakes, continue at speed, or accelerate, just as he desires. Such automatic removal of speed restrictions follows from the fact that, as soon as the auxiliary relays in an occupied block or the track relays when the next block in advance is occupied are picked up, the coils 10 of the track element T or T, as the case may be, are placed in a closed circuit of low resistance and therefore put this track element in its ineffective con dition, thereby not affecting the car apparatus passing suchcontrol point.

The foregoing explanation, based upon the assumption that the danger condition in question is due to the presence of another train ahead in the same block, is also true in case the danger condition is due to a broken rail or the like. If there is a broken rail, the track circuitcurrent from the track battery 4- is interrupted at all points in the rear of the point of breakage, and consequently, all of the auxiliary relays 7 in the rear of the point of breakage can not be energized, with the result that the minimum speed restriction is enforced by the track elements T and T at all of the control points in the rear of the broken rail, in the manner previously explained. Similarly, if a switch is open, the track circuit current being taken through switch box contacts, the auxiliary relays 7 in the rear of this open switch are deprived of current, and the de sired minimum speed restriction is enforced. It will be evident that other hazardous conditions, such as the presence of the car on the detecting circuit at the fouling point of a switch, an open draw bridge,a landslide or other obstruction on the track shunting the track circuit, will establish and maintain the desired minimum speed restriction up to the point of hazard. Likewise, the automatic removal or discontinuation of the minimum speed limit, all explained with the presence of another train in the same block, is true in the case of the other hazards which make the block in question a. danger block. This important characteristic is due, according to this invention, to the fact that the controlling condition of the minimum speed track devices T is determined by the flow of track circuit current in the track rails, down one rail and up the other so as to be shunted out by a car or train ahead, as well as interrupted by a broken rail, open switch box contacts, and the like.

While the auxiliary relays 7, ener ized by the flow of tr: ck circuit current and responsive to the existence of a hazard in the same block, have been shown and described, in the particular embodiment of the invention selected for this disclosure, as opening and closing the circuit of the coil 10 of the track element T which, in cooperation with another track element T and suitable mechanism on the car, enforces a predetermined speed limit without the use of a speed. responsive device on the car, it should be understood that the same underlying principles and characteristics of the invention in connection with the control of the track element T may be employed in other types of systems, such as those using a centrifugal speed responsive device on the car, this device and associated parts being put in condition at the entrance to a danger block to prescribe a minimum speed that continues; until released by a track device controlled by an auxiliary relay 7. In short, that principle or-conception of the invention, which may be briefly stated to reside in the utilization of track circuit current to control the condition of intermitten track de vices, is not limited in its application to the specific type of speed control system shown and described and may be employed to advantage in various other types of systems, either for imposing at that particular control point the desired speed limit or for continuing or discontinuing a minimum speed limit previously set up upon the entrance to the train into the danger block.

In order to explain the nature and mode of this invention, and the functions and mode of operation of the means constituting the same, there has been shown and described one typical embodiment thereof which has been selected more with a view of facilitating explanation .of the invention, ban for the purpose of disclosing the specific structure and arrangement of parts and circuits preferably employed in practice; and it should be understood that various adaptations, modifications and additions may be made to this particular disclosure without departing from the invention. For example, the design and operating charac teristics of the auxiliary relays 7 conforms with recognized track circuit practice. Also, it is contemplated that the system may be used in conjunction with any suitable or well-known type of block signal system, either direct current or alternating current, that various forms and types of sources of electrical energy involved in the car operation may be employed, and that various forms of time control mechanism, and of mechanism for controlling the application of the. brakes and the supply of propelling power may be used and governed in the same way as the train control device K, such brake control mechanism being of course designed to effect an automatic brake application that can not be forestalled or prevented by the engineer, and in a. manner conforming with recognized air brake practice.

Other deviations from the specific disclosure will be evident to those skilled in the art; and I desire to have it understood that the specific structure shown and described is merely illustrative, and does not exhaust the various embodiments thereof.

What I claim as new and desire to secure by Letters Patent ot the United States, is

1. In an automatic train control system of the intermittent inductive type for railroads having tracks divided into blocks, the combination of trackway means located at a plurality of points in each block along the track, of car-carried means adapted to cooperate with and to be inductively influenced by said trackway means through an intervening air-gap to enforce predetermined speed limits dependent upon the condition of said trackway means when passing a control point, and means dependent for their operation on both the traific condition in the block next in advance of the block occupied by the train and on the traffie condition in advance of such point only in such occupied block for governing said trackway means.

2. In an automatic train control system for railroads having tracks divided into blocks, the combination of trackway de vices located at a plurality of points in each block, each of said devices comprising a plurality of track elements, car-carried means adapted to cooperate with said trackway device to apply the brakes of the train if two successive active track elements are passed over in less than a predetermined period of time, and means governed by both traffic conditions in the block next in ad- Vance and by traific conditions in advance in the same block for maintaining said track elements in an active or inactive condition to enforce either caution or danger speed limits.

3. In a train control system for railroads having tracks divided into blocks including means for controlling the movement of a train in a block in accordance with the presence or absence of another train in advance of said train in the same block comprising, a track circuit having the usual source of energy near one end and a track relay at the other and provided with a plurality of auxiliary relays at successive points along the track connected in the track circuit in series with the rails so that these auxiliary relays will be successively dcenergized as a train moves through the block in the direction toward the source of energy, a plurality of trackway devices each located directly in the rear of its corresponding auxiliary relay and maintained active or inactive by said auxiliary relay, and car-carried means cooperating with said trackway means to control the movement of the train in accordance with the condition of said trackway means.

4. Trackway equipment for enforcing speed restrictions through a block and adapted for the control of car equipment for train control systems comprising, pairs of track elements spaced relatively close together and located at intervals in the block, one element of each pair having its controlling condition governed in accordance with the presence or absence of trains only in the same block but in advance of the train to be governed.

5. In a train control system, the combination with brake control apparatus on a vehicle adapted to cause an automatic brake application as two successive influences are communicated from the trackway in less than a predetermined interval of time, pairs of track elements located at control pointsalong the track and spaced apart a distance corresponding to the speed limit desired to be established at each particular control point, and means for controlling one track element of each pair in accordance with the presence or absence of trains in said same block but in advance of said pair.

6. In a train control system, automatic brake control means on a train adapted to be operated at control points in a block when said block is occupied by another train in advance of said first mentioned train, said operation occurring only if the vehicle exceeds a predetermined speed limit at any one of said control points determined by the spacing of trackway devices, and means for automatically rendering said trackway devices ineffective when the portion of the block in advance of the first mentioned train becomes unoccupied.

7. In a train control system, the combination with brake control apparatus on a train adapted to cause an automatic brake application if two successive influences are communicated from the trackway in less than a predetermined interval of time, track elements in groups of threes located at control points along the track in each block, the first and third track element of each group being spaced apart a distance corresponding to' the speed the train is permitted to travel at the-particular control point when the next block in advance is occupied and the first and second track element of each group being spaced'apart a distance corresponding to the speed the train is permitted to travel when said block is occupied by another train in advance of said first mentioned train.

8. Trackway equipment for automatic train control systems comprsiing, track rails divided into blocks 'by insulated joints, a track relay at the entrance and a source of energy at the exit end of each'block, auxiliary electro-responsive devices located at successive points along the track and respon sive to the flow of current at such points in the track rail, and a trackway element directly in the rear of each of the associated points controlled by said auxiliary electroresponsive device in accordance with the presence or absence of a train in advance of said point in the same block.

9. In a train control system, the combination with brake control apparatus on a vehicle including a time controlled device and effective to produce an automatic brake application if two successive control influences are received from the trackway in less than a predetermined interval of time, three track devices spaced along the track and defining two different spaced intervals corresponding to speed limits for caution and for danger, one of said track devices being governed in accordance with trafiic conditions in the next block in advance, and another track device being governed in accordance with traffic conditions in the same block.

10. In a train control system, the combination with brake control apparatus on a vehicle including a time controlled device and effective to produce an automaticbrake application if two successive control influences are received from the trackway in less than a predetermined interval of time, three track devices spaced along the track and de fining two different spaced intervals corre-v sponding to speed limits for caution and stop, each of said track devices having a magnetic core, a second and third track device each having a winding on its core, and

automatic means for closing the windingiof the second track device in a circuit of low resistance dependent upon traffic conditions in the same block and for closing the winding of thethird track device in a circuit of low resistance dependent upon trafiic conditions in the next block in advance.

11. In a train control system, the combination with brake control apparatus on a vehicle including a time controlled device and effective to produce an automatic brake application if two successive control influencesare received on the 'trackway in less than a predetermined interval of time, a pair of track devices in each block, the second device in the direction of normal movement of the trains being normally ineffective and beingautomatically rendered effective by the passage of a vehicle thereby until such vehicle has left the same block.

12. A train control system of the intermittent inductive type comprising, inductive track devices at intervals in each block Which are normally inactive and which act to transmit influences inductively to car-carried means through an interveningair-gap when active, and automatic means for rendering only the devices behind a train in the sanic block active. I

13. In an automatic train control system, the combination with a plurality of track devices located at spaced control points in each block and each active to communicate a stopping influence when there is a train ahead of such point in the same block, and automatic means governed solely by the flow of current in the track rails in advance of such point in such block for rendering the track devices at such point inactive.

14. In a train control system, the combination with a block, a track deviceat an in termediate point in the block comprising, a magnetic core, a winding thereon. acircuit for said winding, and means for'closing the circuit only if there is no train in the same block in advance of said track device regardless of the presence of a train in the rear of said track device in the same block.

15. In a train control system, a track device at an intermediate point in a block adapted to act in cooperation with other trackway means and car-carried apparatus to enforce a predetermined low speed limit on a train when passing such point and means requiring the flow of track circuit current ahead of said train in the same block when the car-carried apparatus is in cooperation with said trackway' device for conditioning said track device to remove said speed limit.

16. In a train control systemthe combination of a track divided into blocks by insulating joints and means for enforcing speed restrictions in a danger block comprising a track device at an intermediate point in that block, an insulated oint in one of the track rails directly ahead of said device, and a relay bridging said joint and at times energized by track circuit current for controlling the operating condition of said device.

17. In a system of train control, the combination with zit block having a normally closed track circuit, a track element at an intermediate point in the block having a mag netic core and a coil thereon, a circuit for saidcoil, and means for closing said circuit if track circuit current is flowing in the track rails just ahead of said element and regardless of whether or not the track circuit in the rear of said element is occupied by a train.

18. A group of track devices for regulating the speed of railway vehicles for both caution and danger trafiic conditions at a control point in a block by the cooperation with receiving means on the vehicle and a time measuring device, said group comprising three track devices, the first encountered by the vehicle being in the active stopping condition under both caution and danger traffic conditions, another being in the active stopping condition if the block next in advance is occupied, and the third being in an active stopping condition if the same block is occupied.

19. The method of train control which consists in enforcing either a caution or a danger speed limit for vehicles at each ofa plurality of control points in a block, dependent on whether there is another train in the next block in advance or in the same block, by applying the brakes of a vehicle automatically if it takes less than a predetermined time in traveling a predetermined distance of travel at said control points.

20. The method of regulating the speed of vehicles in danger blocks for train control purposes which consists in determining intermittently at a plurality of points in each block if the actual speed of the vehicle exceeds a predetermined minimum, by the action of trackway means having its controlling condition dependent upon the flow of track circuit current in the track rails, whereby such minimum speed restrictions will be imposed automatically if there is another train ahead in the same block, or a broken rail, or other hazardous condition capable of affecting the flow of track circuit current is present.

21. In a train control system of the character described, automatic brake control means partly on the car and partly on the track for enforcing predetermined speed restrictions for caution and for danger at control points in each block, and track circuit control means for governing said brake controlling means, the speed limits enforced by said brake controlling means being ant-omatically changed from danger to caution or from caution to clear upon removal of danger conditions ahead in the same block.

22. A train control system of the character described, characterized by the enforcement of either caution or danger speed limits at a plurality of control points in each block, and the automatic discontinuation of said speed limits upon the change of traffic conditions from danger to caution when the advance portion of the block the train in question is occupying clears up and from caution to clear when the block next in advance clears up.

2-3. In a train control system, the combination with a normally closed track circuit, of a relay at an intermediate point in the block affected by the flow of track circuitcurrent in the track rails at such point regardless of whether the track circuit is occupied by another train in the rear of said point, and means governed by said relay for communicating control influences to a passing vehicle in the rear of said point.

24. In a train control system, the combination with a block having a normally closed track circuit, a track device at an intermediate point in the block, a control circuit therefor, and a relay for opening and closing said circuit governed by the How of track circuit current in the track rails in advance of said track device only and independently of whether or not said track circuit is occupied by another train in the rear of said intermediate point.

25. Trackway apparatus for automatic train control systems comprising, a trackway divided into blocks by insulating joints each including the usual source of energy and a track relay, means for enforcing caution speed restrictions in accordance with the conditions of the track relay in the block next in advance, and means for enforcing danger speed restrictions in a block in accordance with the flow of track circuit current in such block ahead of a train already occupying said block, said last mentioned means including a relay connected in series with the track rails at a point ahead of the train.

26. An automatic train control system comprising, means for restricting the speed of the train upon entering a block to a caution value if the next block in advance is occupied and restricting the speed of the train to a lower Value when the block it is entering is occupied by another train ahead, said means including means located at a plurality of control points in a block for relieving the train of such caution restriction if the block in advance clears up and for relieving the train of the danger restriction if the portion in advance of the train of the block occupied by the train clears up.

27. An automatic train control system for railways having tracks divided into blocks each having a closed track circuit including a normally energized track relay and in which control influences are transmitted from the track to the vehicle intermittently comprising, car-carried apparatus for restricting the speed of the train in accordance with the reception of control influences from the trackway limiting the train either to a caution speed or a danger speed, and trackway means located at a plurality of points in each block for transmitting control influences to the train depending on whether the block in advance of the block the train is moving in its occupied or whether the portion of the block ahead of the train is occupied, whereby if adanger speed restriction has been effected the clearing of the portion ahead of a train 1n the same block causes the danger restriction to be removed upon passing a control point and whereby both the danger and the cantion restriction will be removed upon passing a control point if the portion in advance of the train of the block the train is occupying and the next block in advance clear up regardless of whether the portion of the block in the rear of the train is occupied.

28. An automatic train controlsystem of the intermittent time-distance interval speed control type comprising, car-carried apparatus constructed and arranged to automaticallv applv the brakes if a car on which it is mounted passes two active trackway devices in less than a predetermined time, pairs of trackway devices tending to assume an active condition located at success ve points in a block of the usual closed track circuit type, and means for making pair of these trackway devices inactive it the portion of the track circuit in advance of such pair is unoccupied regardless of whether the portion of the track circuit in the rear of such pair of devices is occupied and for making another pair of these trackway devices inactive if the track circuit of the next block in advance is unoccupied and is not dangerous for some other reason.

29. Trackway apparatus for automatic train control systems comprising, a track divided into blocks each provided with the usual closed track circuit including a track relay and a source of energy, influence communicating means located at a plurality of points in each block each of said means including a circuit which it broken places said means in a condition to transmit an unfavorable control influence, and means associated with the block in which a particular influence communicating means is located and the block in advance thereof for breaking a circuit associated with said means if the block in advance is occupied or the advance portion of th same block is occupied and regardless of whether the portion in the rear of said control means of said block is occupied.

30. Trackway apparatus for automatic train control systems comprising, a track divided into blocks each provided with the usual closed track circuit including a track relay and a source of energy, influence communicating means located at a plurality oi? points in each block each of said means being constructed on the closed circuit principle so that the interruption of a circuit associated therewith causes the t 'ansmisison of unfavorable control influences, and means for opening a circuit associated with such influence communicating means in a block it any portion in advance in the same block is occupied by another train regardless of whether the portion of the block in the rear thereof is occupied, or if the next block in advance of said block is occupied.

31. Signal control apparatus for railways comprising, a railway track divided into blocks by insulating joints each of which includes the usual track relayv connected across the rails near the entrance end of the block, a source of energy connected across the rails near the exit end of the block and a plurality of relay windings connected in series with the rails of the trackway and located at successive intermediate control points in each block, and means associated with the apparatus at each control point for indicating whether the portion of the block in advance of such control point of the same block is occupied or is dangerous for some other reason and regardless of whether the portion of the block in the rear of such point is occupied, whether the next block in advance is occupied or is dangerous, or whether both of these trackway portions are clear. a

32. Signal control apparatus for railway signaling systems comprising, a railway track divided into blocks by insulating joints in the usual manner each of which includes a source of energy connected across the rails at the exit end of the block and a track relay connected across the rails at the entrance end thereof and a plurality of series track relays connected in series with the track rails one at each of a plurality of control points in each block, and means located at each of said control points which assume a particular conditionif either the series track relay at said control point is de-energized or the track relay of the next block in advance is de-energized,' whereby the condition of traffic of a portion of a block and a whole block adjacent thereto may be ascertained.

33. Trackway apparatus for automatic train control systems comprising; a railway track divided into blocks by insulating joints in the usual manner each of which includes a source of energy connected across the rails at the exit end of the block, a track relay connected across the rails at the entrance of the block, and a plurality of series track relays connected in series with the track rails one at each of a plurality of control points; and influence communicating means located at each control point conditioned if either the series relay at such control point is deenergized, or the track relay of the next 10 block in advance is de-energized; whereby the condition of traffic of a portion of one block and a Whole block adjacent thereto may be communicated to a train.

In testimony whereof I hereby afi ix my signature.

lVINTI-IROP K. HOlVE. 

